Dozens of copper coils in an MRI scanner pick up the faint response from tissues, like microphones trying to catch a whisper in a noisy hall. Each microphone drags a thick bundle of wires behind it. The wires press on each other, create electrical interference, heat up, and add risk for the patient.
A team of researchers proposed replacing that copper tangle with optical fibers. In the Light Coils architecture, the signal from each coil is converted into light using a Mach-Zehnder modulator — a tiny device that varies the brightness of a laser beam in sync with the radio signal. Power for the preamplifiers is delivered over the same fiber: a powerful laser lights a photovoltaic cell, turning light into electricity. Even the coil's detuning during the scanner's RF pulse is triggered by an optical command — no galvanic connection at all.
Tests on a clinical 3 Tesla scanner showed that a single "light coil" produces brain images of a living human that are indistinguishable in quality from the traditional coaxial connection. Moreover, signals from four coils were transmitted over a single fiber by wavelength-division multiplexing, like different colors in a rainbow. The optical isolation between channels exceeded 28 decibels, and noise correlation was lower than with the copper counterpart.
This opens the path to lightweight, modular, and potentially ultra-dense receiver coil arrays based on integrated photonics. Instead of a heavy bundle of cables — a few transparent threads. Instead of electrical interference — pure light. Now the whisper in the hall can be listened to with dozens of microphones, without fear of them tangling in their own wires.
An optical fiber as thin as a human hair can transmit data at rates up to several terabits per second — thousands of times faster than a copper cable of the same thickness.